Zwitterionic Phosphorus Ylide Adducts of Boron‐Bridged ansa ‐Zirconocene Complexes as Precatalysts for Olefin Polymerization

Autor: Xiaoping Jin, Pamela J. Shapiro, Feilong Jiang, Brendan Twamley, Arnold L. Rheingold, Jasson T. Patton
Rok vydání: 2004
Předmět:
Zdroj: European Journal of Inorganic Chemistry. 2004:3370-3378
ISSN: 1099-0682
1434-1948
DOI: 10.1002/ejic.200300932
Popis: Methylenetriphenylphosphorane was coordinated to the boron of phenylborylidene-bridged bis(cyclopentadienyl)- and bis(2-Me,4-Ph-indenyl)zirconium dichloride to form zwitterionic ansa-zirconocene complexes. The cyclopentadienyl complex 2, when activated with MAO, exhibits remarkable polymerization activity that is more than an order of magnitude greater than that of a related amidoborylidene-bridged complex as well as the commercially important precatalyst [Cp′−SiMe2−N−tBu]TiCl2 (Cp′ = C5Me4). The zwitterionic bis(2-Me,4-Ph-indenyl)zirconium dichloride species is isolated as a mixture of rac and meso isomers 4−6. The propylene polymerization efficiency of the isomer mixture activated by MAO is greater than that of a related silylene bridged system at 70 and 85 °C; however, the activity of the zwitterionic system decreased with further increase in temperature. The high level of isotactic triads (63.6%) and pentads (52.4%) in the polypropylene formed by 4−6 indicates that the rac isomer is the most active precatalyst of the mixture. The molecular structures of 2 and the rac bis-indenylzirconium isomer 4 and one of the meso isomers 5 are described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Databáze: OpenAIRE
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